Transmitting spread signal in communication system

ABSTRACT

The present invention provides for transmitting a spread signal in a mobile communication system. The present invention includes spreading a signal using a plurality of spreading codes, wherein the plurality of spreading codes have a spreading factor, multiplexing the spread signal by code division multiplexing, transmitting the multiplexed signal via a plurality of neighboring frequency resources of one OFDM symbol of a first antenna set, and transmitting the same multiplexed signal via a plurality of neighboring frequency resources of one OFDM symbol of a second antenna set.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/045,455, filed on Mar. 10, 2011, currently pending, which is acontinuation of U.S. patent application Ser. No. 12/139,254, filed onJun. 13, 2008, now U.S. Pat. No. 7,953,169, which claims the benefit ofearlier filing date and right of priority to Korean Patent ApplicationNo. 10-2007-122986, filed on Nov. 29, 2007, and also claims the benefitof U.S. Provisional Application Serial No. 60/943,783, filed on Jun. 13,2007, 60/955,019, filed on Aug. 9, 2007, 60/976,487, filed on Oct. 1,2007, 60/982,435, filed on Oct. 25, 2007, and 60/983,234, filed on Oct.29, 2007, the contents of which are all hereby incorporated by referenceherein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication system, and moreparticularly, to transmitting a spread signal in a communication system.

2. Discussion of the Related Art

Recently, the demand for wireless communication services has risenabruptly due to the generalization of information communicationservices, the advent of various multimedia services and the appearanceof high-quality services. To actively cope with the demand, acommunication system's capacity should first be increased. In order todo so, methods for finding new available frequency bands and raising theefficiency of given resources in wireless communication environments areconsidered.

Much effort and attention has been made to research and developmulti-antenna technology. Here, diversity gain is obtained byadditionally securing a spatial area for resource utilization with aplurality of antennas provided to a transceiver or raising transmissioncapacity by transmitting data in parallel via each antenna.

An example of a multi-antenna technology is a multiple input multipleoutput (MIMO) scheme. The MIMO scheme indicates an antenna system havingmultiple inputs and outputs, raises a quantity of information bytransmitting different information via each transmitting antenna, andenhances reliability of transport information using coding schemes suchas STC (space-time coding), STBC (space-time block coding), SFBC(space-frequency block coding) and the like.

SUMMARY OF THE INVENTION

The present invention is directed to transmitting a spread signal in amobile communication system.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method for transmitting a spread signal in amobile communication system, the method comprising spreading a signalusing a plurality of spreading codes, wherein the plurality of spreadingcodes have a spreading factor, multiplexing the spread signal by codedivision multiplexing, transmitting the multiplexed signal via aplurality of neighboring frequency resources of one OFDM symbol of afirst antenna set, and transmitting the same multiplexed signal via aplurality of neighboring frequency resources of one OFDM symbol of asecond antenna set.

Preferably, the multiplexed signal is transmitted on four neighboringfrequency resources. Preferably, the spreading factor is 4.Alternatively, the spreading factor is equal to the number ofneighboring frequency resources.

In one aspect of the present invention, the first antenna set is spacefrequency block coded by applying a space frequency block code to eachneighboring pair of frequency resources of one OFDM symbol, wherein thefirst antenna set comprises two antennas. Moreover, the second antennaset is space frequency block coded by applying a space frequency blockcode to each neighboring pair of frequency resources of one OFDM symbol,wherein the second antenna set comprises two antennas.

Preferably, the multiplexed signal transmitted via the first antenna setand the multiplexed signal transmitted via the second antenna set aretransmitted via respectively different frequency resources. Preferably,the multiplexed signal transmitted via the first antenna set and themultiplexed signal transmitted via the second antenna set aretransmitted via respectively different OFDM symbols.

In another aspect of the present invention, the multiplexed signal istransmitted alternately by the first antenna set and second antenna setvia independent frequency resources repeatedly. Preferably, themultiplexed signal is transmitted a total of 3 times using the firstantenna set and second antenna set alternately.

In one aspect of the present invention, the first antenna set comprisesa first antenna and a second antenna of a four-antenna group, and thesecond antenna set comprises a third antenna and a fourth antenna of thefour-antenna group.

In another aspect of the present invention, the first antenna setcomprises a first antenna and a third antenna of a four-antenna group,and the second antenna set comprises a second antenna and a fourthantenna of the four-antenna group.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme in a communication system in accordance with oneembodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with one embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with one embodiment of the present invention.

FIG. 4 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with one embodiment of the present invention.

FIG. 6 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a method for transmittinga spread signal via a plurality of OFDM symbols in accordance with oneembodiment of the present invention.

FIG. 8 is a diagram illustrating an example of a method for transmittinga spread signal via a plurality of OFDM symbols in accordance with oneembodiment of the present invention, in which an SFBC/FSTD scheme isapplied to the spread signal.

FIG. 9 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with one embodiment of the present invention.

FIG. 10 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention.

FIG. 11 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention.

FIG. 12 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention.

FIG. 13 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to at least one spread signal in a communication systemin accordance with one embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of a method fortransmitting a spread signal in a mobile communication system inaccordance with one embodiment of the present invention.

FIG. 15 is a diagram illustrating an example of a method for receiving aspread signal in a mobile communication system in accordance with oneembodiment of the present invention.

FIG. 16 is a diagram illustrating an example of a base station and auser equipment in a mobile communication system in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to transmitting a spread signal in awireless communication system.

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. It is to be understood that the following detailed descriptionof the present invention is exemplary and explanatory and is intended toprovide further explanation of the invention as claimed. The followingdetailed description includes details to provide complete understandingof the present invention. Yet, it is apparent to those skilled in theart that the present invention can be embodied without those details.For instance, predetermined terminologies are mainly used for thefollowing description, need not to be limited, and may have the samemeaning in case of being called arbitrary terminologies.

To avoid vagueness of the present invention, the structures or devicesknown in public are omitted or depicted as a block diagram and/orflowchart focused on core functions of the structures or devices.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

For the following embodiments, elements and features of the presentinvention are combined in prescribed forms. Each of the elements orfeatures should be considered as selective unless there is separate andexplicit mention. Each of the elements or features can be implementedwithout being combined with others. And, it is able to construct anembodiment of the present invention by combining partial elements and/orfeatures of the present invention. The order of operations explained inthe following embodiments of the present invention can be changed. Somepartial configurations or features of a prescribed embodiment can beincluded in another embodiment and/or may be replaced by correspondingconfigurations or features of another embodiment.

In this disclosure, embodiments of the present invention are describedmainly with reference to data transmitting and receiving relationsbetween a base station and a terminal. In this case, the base stationhas a meaning of a terminal node of a network, which directly performscommunication with the terminal. In this disclosure, a specificoperation described as performed by a base station can be carried out byan upper node of the base station. Namely, it is understood that variousoperations carried out by a network, which includes a plurality ofnetwork nodes including a base station, for the communication with aterminal can be carried out by the base station or other network nodesexcept the base station. “Base station” can be replaced by such aterminology as a fixed station, Node B, eNode B (eNB), access point andthe like. And, “terminal” can be replaced by such a terminology as UE(user equipment), MS (mobile station), MSS (mobile subscriber station)and the like.

FIG. 1 is a diagram illustrating an example of a method of applying anSFBC/FSTD scheme in a wireless communication system, in accordance withone embodiment of the present invention. In FIG. 1, a method forobtaining 4-degree transmitting antenna diversity is implemented using aplurality of transmitting antennas, e.g., four downlink transmittingantennas of a communication system. Here, two modulation signalstransmitted via two adjacent subcarriers are transmitted via a firstantenna set including two antennas by having space frequency blockcoding (SFBC) applied thereto. Two SFBC-coded subcarrier sets aretransmitted via two different antenna sets each including two differentantennas by having frequency switching transmit diversity (FSTD) appliedthereto. As a result, a transmitting antenna diversity degree 4 can beobtained.

Referring to FIG. 1, a single small box indicates a single subcarriertransmitted via a single antenna. The letters “a”, “b”, “c” and “d”represent modulation symbols modulated into signals differing from eachother. Moreover, functions f₁(x), f₂(x), f₃(x) and f₄(x) indicate randomSFBC functions that are applied to maintain orthogonality between twosignals. These functions can be represented as in Equation 1.

f ₁(x)=x, f ₂(x)=x, f ₃(x)=−x*, f ₄(x)=x*   [Equation 1]

Despite two signals being simultaneously transmitted via two antennasthrough the random SFBC function applied to maintain orthogonalitybetween the two signals, a receiving side may be able to obtain anoriginal signal by decoding each of the two signals. In particular, FIG.1 shows a structure that SFBC and FSTD transmitted in downlink within arandom time unit is repeated. By applying a simple reception algorithmthat the same SFBC decoding and FSTD decoding are repeated in areceiving side through the structure of SFBC and FSTD repeatingtransmissions, decoding complexity is reduced and decoding efficiency israised.

In the example shown in FIG. 1, modulated symbol sets (a, b), (c, d),(e, f) and (g, h) become an SFBC-coded set, respectively. FIG. 1 showsthat subcarriers having SFBC/FSTD applied thereto are consecutive.However, the subcarriers having SFBC/FSTD applied thereto may notnecessarily be consecutive in a frequency domain. For instance, asubcarrier carrying a pilot signal can exist between SFBC/FSTD appliedsubcarriers. Yet, two subcarriers constructing an SFBC coded set arepreferably adjacent to each other in a frequency domain so that wirelesschannel environments covered by a single antenna for two subcarriers canbecome similar to each other. Hence, when SFBC decoding is performed bya receiving side, it is able to minimize interference mutually affectingthe two signals.

In accordance with one embodiment of the present invention, an SFBC/FSTDscheme may be applied to a spread signal sequence. In a manner ofspreading a single signal into a plurality of subcarriers through(pseudo) orthogonal code in a downlink transmission, a plurality ofspread signals may be transmitted by a code division multiplexing (CDM)scheme.

For example, when attempting to transmit different signals “a” and “b”,if the two signals are to be CDM-transmitted by being spread by aspreading factor (SF) 2, the signal a and the signal b are transformedinto spread signal sequences (a·c₁₁, a·c₂₁) and (b·c₁₂, bc₂₂) using(pseudo) orthogonal spreading codes of two chip lengths (c₁₁, c₂₁) and(c₁₂, c₂₂), respectively. The spread signal sequences are modulated byadding a·c₁₁+b·c₁₂ and a·c₂₁+b₂₂ to two subcarriers, respectively.Namely, a·c₁₁+b·c₁₂ and a·c₂₁+bc₂₂ become modulated symbols,respectively. For clarity and convenience, the spread signal sequenceresulting from spreading the signal a by SF=N is denoted as a₁, a₂, . .. , a_(N).

FIG. 2 is a diagram illustrating an example of a method of applying anSFBC/FSTD scheme to a spread signal in a communication system, inaccordance with one embodiment of the present invention. In order todecode a signal spread over a plurality of subcarriers by despreading ina receiving side, as mentioned in the foregoing description, it ispreferable that each chip of a received spread signal sequence undergo asimilar wireless channel response. In FIG. 2, four different signals a,b, c and d are spread by SF=4 and the spread signals are transmitted bySFBC/FSTD through four subcarriers explained in the foregoingdescription of FIG. 1. Assuming that the function explained for theexample in Equation 1 is used as an SFBC function, a received signal ineach subcarrier can be represented as in Equation 2.

Subcarrier 1: h₁(a₁+b₁+c₁+d₁)−h₂(a₂+b₂+c₂+d₂)*

Subcarrier 2: h₁(a₂+b₂+c₂+d₂)+h₂(a₁+b₁+c₁+d₁)*

Subcarrier 3: h₃(a₃+b₃+c₃+d₃)−h₄(a₄+b₄+c₄+d₄)*

Subcarrier 4: h₃(a₄+b₄+c₄+d₄)+h₄(a₃+b₃+c₃+d₃)*   [Equation 2]

In Equation 2, h_(i) indicates fading undergone by an i^(th) antenna.Preferably, subcarriers of the same antenna undergo the same fading. Anoise component added to a receiving side may be ignored. And, a singlereceiving antenna preferably exists. In this case, spread sequencesobtained by a receiving side after completion of SFBC decoding and FSTDdecoding can be represented as in Equation 3.

(|h₁|²+|h₂|²)·(a₁+b₁+c₁+d₁),

(|h₁|²+|h₂|²)·(a₂+b₂+c₂+d₂),

(|h₃|²+|h₄|²)·(a₃+b₃+c₃+d₃),

(|h₃|²+|h₄|²)·(a₄+b₄+c₄+d₄),   [Equation 3]

Here, in order to separate the spread sequence obtained by the receivingside from the signals b, c and d by despreading with a (pseudo)orthogonal code corresponding to the signal a for example, the wirelesschannel responses for the four chips is preferably the same. However, ascan be observed from Equation 3, signals transmitted via differentantenna sets by FSTD are (|h₁|²+|h₂|²) and (|h₃|²+|h₄|²) and provideresults through different wireless channel responses, respectively.Thus, complete elimination of a different CDM-multiplexed signal duringdispreading is not performed.

Therefore, one embodiment of the present invention is directed to amethod of transmitting at least one spread signal in a communicationsystem, wherein each of at least one signal is spread by (pseudo)orthogonal code or the like with a spreading factor (SF), and whereinthe at least one spread signal is multiplexed by CDM and transmitted viathe same antenna set. FIG. 3 is a diagram illustrating an example for amethod of applying an SFBC/FSTD scheme to a spread signal in acommunication system in accordance with one embodiment of the presentinvention. In the present embodiment, each of at least one signal isspread by (pseudo) orthogonal code or the like with SF=4. Furthermore,the at least one spread signal is multiplexed and transmitted by CDM,and the multiplexed signals are transmitted via the same antenna set.

In FIG. 3, when a total of four transmitting antennas are used, a firstantenna set includes a first antenna and a second antenna. A secondantenna set includes a third antenna and a fourth antenna. Inparticular, each of the first and second antenna sets is the antenna setfor performing SFBC coding, and an FSTD scheme is applicable between thetwo antenna sets. According to the present embodiment, assuming thatdata to be transmitted is carried by a single OFDM symbol, the signalspread with SF=4, as shown in FIG. 3, can be transmitted via fourneighbor subcarriers of one OFDM symbol via the same SFBC-coded antennaset.

In FIG. 3( a), shown is a case where the spread signal transmitted viathe first antenna set is different from the spread signal transmittedvia the second antenna set. In FIG. 3( b), shown is a case where thespread signal transmitted via the first antenna set is repeatedlytransmitted via the second antenna set to obtain a 4-degree transmittingantenna diversity gain.

FIG. 4 is a diagram illustrating another example for a method ofapplying an SFBC/FSTD scheme to a spread signal in a communicationsystem in accordance with one embodiment of the present invention. Inthe present embodiment, like the former embodiment shown in FIG. 3, eachof at least one signal is spread by (pseudo) orthogonal code or the likewith SF=4. The at least one spread signal is multiplexed and transmittedby CDM, and the multiplexed signals are transmitted via the same antennaset.

In FIG. 4, unlike FIG. 3, when a total of four transmitting antennas areused, a first antenna set includes a first antenna and a third antenna.A second antenna set includes a second antenna and a fourth antenna.Namely, compared to FIG. 3, FIG. 4 shows a case of using a differentmethod for constructing each antenna set but applying the same SFBC/FSTDscheme. Here, according to the present embodiment, the signal spreadwith SF=4 can be transmitted via four neighbor subcarriers of one OFDMsymbol via the same SFBC-coded antenna set.

In FIG. 4( a), shown is a case where the spread signal transmitted viathe first antenna set is different from the spread signal transmittedvia the second antenna set. In FIG. 4( b), shown is a case where thespread signal transmitted via the first antenna set is repeatedlytransmitted via the second antenna set to obtain a 4-degree transmittingantenna diversity gain.

FIG. 5 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with an embodiment of the present invention. Preferably, asame signal can be repeatedly transmitted to obtain additionaldiversity. Accordingly, the present embodiment relates to a case wherethe same signal is repeatedly transmitted at least twice via differentsubcarriers on a frequency axis, i.e., for a period of the same timeunit.

In the present embodiment, an antenna set is determined as follows.First, after a signal has been spread with SF=4, an antenna set isdetermined by a 4-subcarrier unit to enable the signal spread accordingto the aforesaid embodiment to be transmitted via the same antenna set.In this case, as mentioned in the foregoing description, the signal isrepeatedly transmitted by changing an antenna set in case of repetitivetransmission to apply the SFBC/FSTD scheme for obtaining 4-degreetransmitting antenna diversity. According to the present embodiment, anantenna-frequency mapping structure, to which the SFBC/FSTD scheme forobtaining 4-degree transmitting antenna diversity gain is applied, maybe repeated by an 8-subcarrier unit.

In FIG. 5( a), shown is an example where the repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 3.In FIG. 5( b), shown is an example where the repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 4.In particular, FIG. 5( a) and FIG. 5( b) show examples for applying theSFBC/FSTD scheme for obtaining 4-degree transmitting antenna diversitygain using eight neighbor subcarriers, respectively. Although FIG. 5( a)and FIG. 5( b) differ from each other with respect to the antennasincluded in the first and second antenna sets, each use the same methodin applying the present embodiment.

In accordance with the present invention, a one-time transmission maycorrespond to a case where a signal having been spread with SF=4 isCDM-multiplexed and then transmitted via four subcarriers. Accordingly,assuming that one-time transmission is performed via the first antennaset shown in FIG. 5( a) or 5(b), a two-time transmission, which is therepetitive transmission of the one-time transmission, can be carried outvia the second antenna set. Thus, it is observed that the SFBC/FSTDscheme is implemented via the one-time transmission and the two-timetransmission. In the same manner, a three-time transmission may becarried out when the first antenna set performs the transmission again.

FIG. 6 is a diagram illustrating another example for a method ofapplying a SFBC/FSTD scheme to a spread signal in a communication systemin accordance with an embodiment of the present invention. In FIG. 6,like the embodiment shown in FIG. 5, after a signal is spread with SF=4,an antenna set is determined by a 4-subcarrier unit to enable the signalspread according to the aforesaid embodiment to be transmitted via thesame antenna set. In this case, as mentioned in the foregoingdescription, the signal is repeatedly transmitted by changing an antennaset in case of repetitive transmission to apply SFBC/FSTD for obtaining4-degree transmitting antenna diversity.

However, while the embodiments shown in FIG. 5 use the SFBC/FSTD schemethrough eight neighbor subcarriers, the embodiment of FIG. 6 usessubcarriers having an interval compared to a previous transmission.Thus, frequency diversity may be obtained in addition to 4-degreeantenna diversity. Notably, it is preferable that subcarriers throughwhich a spread signal sequence is multiplexed and transmitted includesubcarriers that neighbor each other.

This may be explained as follows. First, a one-time transmission may beperformed using only four of eight subcarriers to which the SFBC/FSTDscheme is applied in the embodiment shown in FIG. 5 using a firstantenna set. Subsequently, the one-time transmission is performed usingfour of eight subcarriers to which the SFBC/FSTD scheme is applied usinga second antenna set. Accordingly, in order to implement the SFBC/FSTDscheme for obtaining 4-degree transmitting antenna diversity, an antennaset different from that of a previous transmission is used.

In FIG. 6( a), shown is an example where a repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 3.In FIG. 6( b), shown is an example where a repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 4.Although FIG. 6( a) and FIG. 6( b) differ from each other with respectto the antennas included in the first and second antenna sets, each usethe same method in applying the present embodiment.

Referring to FIG. 6, compared to the method described in FIG. 5, theembodiment of FIG. 6 may considerably save resources required for therepetitive transmission by reducing additionally used resources in half.Therefore, if the repetitive transmission method according to FIG. 6 isapplied, resources used for data transmission are used more efficiently.

As described above, a method of applying an SFBC/FSTD scheme for asingle time unit according to an embodiment of the present invention wasexplained. However, situations occur where a signal may be transmittedusing a plurality of time units, wherein a single OFDM symbol may bepreferably defined as a time unit in a communication system adoptingorthogonal frequency division multiplexing. Accordingly, in accordancewith an embodiment of the present invention, a method of applying anSFBC/FSTD scheme to a case of transmitting a signal using a plurality ofOFDM symbols will be explained.

When a signal is transmitted via a plurality of OFDM symbols, repetitivetransmission on a time axis as well as a frequency axis is possible toobtain diversity additional to transmitting antenna diversity.Accordingly, CDM and SFBC/FSTD schemes may be applied to a spread signalfor an ACK/NAK signal transmitted in downlink to announce thesuccessful/failed reception of data transmitted in uplink.

FIG. 7 is a diagram illustrating an example of a method for transmittinga spread signal via a plurality of OFDM symbols in accordance with oneembodiment of the present invention. Referring to FIG. 7, each small boxindicates a resource element (RE) constructed with a single OFDM symboland a single subcarrier. A_(ij) may indicate an ACK/NAK signalmultiplexed by CDM, wherein “i” indicates an index of a signal spreadand then multiplexed, and “j” indicates an ACK/NAK channel index of themultiplexed ACK/NAK signal. In this case, an ACK/NAK channel indicates aset of multiplexed ACK/NAK signals. A plurality of ACK/NAK channels mayexist according to necessity and resource situation of each system.However, for clarity and convenience of description, a single ACK/NAKchannel exists in FIG. 7.

In FIG. 7( a), shown is an example where a multiplexed ACK/NAK signal istransmitted via a single OFDM symbol. Referring to FIG. 7( a), fourACK/NAK signals are spread by a spreading factor equal to four (SF=4)for a single OFDM symbol, multiplexed by CDM, and then transmitted viafour neighbor subcarriers. Because a single OFDM symbol is used for theACK/NAK signal transmission, diversity gain on a time axis may not beobtained. However, four repetitive transmissions of the ACK/NAK signalmultiplexed by CDM may be carried out along a frequency axis. Hence, thefour-time repetitive transmission exemplifies repetition to obtaindiversity. Notably, a repetition count may vary according to a channelstatus and/or a resource status of a system.

In FIG. 7( b), shown is an example where a multiplexed ACK/NAK signal istransmitted via a plurality of OFDM symbols. Referring to FIG. 7( b),four ACK/NAK signals are spread by a spreading factor SF=4 for two OFDMsymbols each, multiplexed by CDM, and then transmitted via four neighborsubcarriers. Namely, in case that OFDM symbols for ACK/NAK signaltransmission increase, the ACK/NAK signal may be repetitivelytransmitted using a single OFDM symbol for the increased OFDM symbols asit is. However, when the ACK/NAK signal is repetitively transmitted fora second OFDM symbol, transmission is performed to maximize use ofsubcarriers that are not overlapped with former subcarriers used for thefirst OFDM symbol. This is preferable considering a frequency diversityeffect.

In FIG. 7( b), shown is a case where the number of ACK/NAK signalstransmittable despite the increased number of OFDM symbols is equal tothe case where a single OFDM symbol is used. Previously, an ACK/NAKsignal was transmitted repeatedly only on a frequency axis when using asingle OFDM symbol. However, in accordance with the present embodiment,more time-frequency resources may be used for transmitting the samenumber of ACK/NAK signals as in the single OFDM symbol case bysubstantially incrementing the repetition count of time-frequency. Here,because OFDM symbols used for the ACK/NAK transmission are increased,more signal power used for the ACK/NAK transmission can be allocated.Hence, the ACK/NAK signal may be transmitted to a cell having a widerarea.

In FIG. 7( c), shown is another example where multiplexed ACK/NAKsignals are transmitted via a plurality of OFDM symbols. Referring toFIG. 7( c), when the number of OFDM symbols for ACK/NAK signaltransmission is set at 2, the transmission may be carried out byreducing the frequency-axis repetition count of the ACK/NAK signalmultiplexed by CDM. Thus, by decreasing the repetition count tofacilitate transmission when the number of OFDM symbols is set at 2,resources are efficiently utilized.

Compared with the transmission method shown in FIG. 7( b), fourtime-frequency axis transmission repetitions of the ACK/NAK signal arereduced to two transmission repetitions in FIG. 7( c). However, becausethe number of OFDM symbols used for the ACK/NAK signal transmission isincremented, the transmission method shown in FIG. 7( c) is similar tothe method shown in FIG. 7( a), where a single OFDM symbol is used,because four time-frequency resource areas are available in both themethods shown in FIGS. 7( a) and 7(c).

Furthermore, compared to the transmission method shown in FIG. 7( b),the method shown in FIG. 7( c) may reduce the signal power for ACK/NAKchannel transmission because the number of time-frequency resource areasused for a single ACK/NAK channel transmission is reduced. Moreover,because the ACK/NAK channel is transmitted across the time-frequencyareas, per-symbol transmission power allocation may be performed moreefficiently than transmission over a single OFDM symbol only.

In case that ACK/NAK signals are repetitively transmitted in the samestructure for all OFDM symbols to simplify a system's schedulingoperation, such as when the time-frequency resources shown in FIG. 7( b)are used for example, different ACK/NAK channels may be transmitted. Inparticular, because double ACK/NAK channels are transmittable, moreefficient resource use is achieved.

As described above, a spreading factor for multiplexing a plurality ofACK/NAK signals, a repetition count in time-frequency domain and thenumber of OFDM symbols for ACK/NAK signal transmission, which areexplained with reference to FIG. 7, are exemplarily provided for a moreaccurate description of the present invention. It is understood thatdifferent spreading factors, different repetition counts and variousOFDM symbol numbers are applicable to the present invention. Moreover,the embodiments shown in FIG. 7 may relate to using a singletransmitting antenna that does not use transmitting antenna diversity,but may also be applicable to a 2-transmitting antenna diversity method,4-transmitting antenna diversity method, and the like.

FIG. 8 is a diagram illustrating an example of a method for transmittingspread signals via a plurality of OFDM symbols in accordance with oneembodiment of the present invention, in which an SFBC/FSTD scheme isapplied to the spread signal. Referring to FIG. 8, a 4-degreetransmitting antenna diversity method using a total of four transmittingantennas is implemented. Here, a single ACK/NAK channel exists forclarity and convenience of description.

In FIG. 8( a), an SFBC/FSTD scheme is applied to a spread signal usingfour transmitting antennas, and the signal is transmitted for aplurality of OFDM symbols. Furthermore, four ACK/NAK signals are spreadwith a spreading factor SF=4 for each of two OFDM symbols, multiplexedby CDM, and then transmitted via four neighbor subcarriers. Preferably,when OFDM symbols for ACK/NAK signal transmission increase, the ACK/NAKsignal may be repetitively transmitted using a single OFDM symbol forthe increased OFDM symbols as it is. Notably, this process is similar tothe process described with reference to FIG. 7( b).

However, when a repetitive transmission is performed for a second OFDMsymbol, it is carried out using an antenna set different from an antennaset used for a first OFDM symbol. For example, if a transmission for afirst OFDM symbol is performed using a first antenna set including afirst antenna and a third antenna, a transmission for a second OFDMsymbol can be performed using a second antenna set including a secondantenna and a fourth antenna. Accordingly, the transmission for thesecond OFDM symbol is carried out by maximizing use of subcarriers notoverlapped with former subcarriers used for the first OFDM symbol. Thisis preferable to achieve a frequency diversity effect.

In FIG. 8( b), shown is another example of applying an SFBC/FSTD schemeto a spread signal using four transmitting antennas and transmitting thesignal for a plurality of OFDM symbols in accordance with one embodimentof the present invention. Referring to FIG. 8( b), when the number ofOFDM symbols for ACK/NAK signal transmission is set to 2, the signal maybe transmitted by reducing a frequency-axis repetition count of theACK/NAK signal multiplexed by CDM. Notably, this process is similar tothe method described with reference to FIG. 7( c). However, whenrepetitive transmission is carried out for a second OFDM symbol, thetransmission will be performed using an antenna set different from theantenna set used for the first OFDM symbol.

FIG. 9 is a diagram illustrating an example for a method of applying anSFBC/FSTD scheme to a spread signal in a communication system inaccordance with one embodiment of the present invention. Referring toFIG. 9, when a total of four transmitting antennas are used, a firstantenna set includes a first antenna and second antenna, and a secondantenna set includes a third antenna and fourth antenna. Preferably,each of the first and second antenna sets is an antenna set forperforming SFBC coding and an FSTD scheme applicable between the twoantenna sets. According to the present embodiment, if data istransmitted for a single OFDM symbol, the signal spread with SF=2, asshown in FIG. 9, can be transmitted via two neighbor subcarriers of oneOFDM symbol via the same SFBC-coded antenna set.

In FIG. 9( a), shown is a case where the spread signal transmitted viathe first antenna set is different from the spread signal transmittedvia the second antenna set. In FIG. 9( b), shown is a case where thespread signal transmitted via the first antenna set is repeatedlytransmitted via the second antenna set to obtain a 4-degree transmittingantenna diversity gain.

Accordingly, with regard to FIG. 9, a single signal may be spread withSF=2. Thus, the same structure as applying an SFBC/FSTD scheme by4-subcarrier unit for a CDM-multiplexed signal may be used, but withoutconsidering spreading as in FIG. 1

FIG. 10 is a diagram for illustrating another example of a method forapplying an SFBC/FSTD scheme to spread signals in a communication systemin accordance with one embodiment of the present invention. In theembodiment shown in FIG. 10, like the former embodiment shown in FIG. 9,at least one or more signals are spread by (pseudo) orthogonal code orthe like with SF=2. The at least one or more spread signals are alsomultiplexed and transmitted by CDM. Here, the multiplexed signals aretransmitted via the same antenna set.

In FIG. 10, unlike FIG. 9, when a total of four transmitting antennasare used, a first antenna set includes a first antenna and thirdantenna, and a second antenna set includes a second antenna and fourthantenna. Thus, compared to FIG. 9, FIG. 10 illustrates use of adifferent method for constructing each antenna set but applies the sameSFBC/FSTD scheme. In accordance with the present embodiment, the signalspread with SF=2 may be transmitted via two neighbor subcarriers of oneOFDM symbol via the same SFBC-coded antenna set.

In FIG. 10( a), shown is a case where the spread signal transmitted viathe first antenna set is different from the spread signal transmittedvia the second antenna set. In FIG. 10( b), shown is a case where thespread signal transmitted via the first antenna set is repeatedlytransmitted via the second antenna set to obtain a 4-degree transmittingantenna diversity gain.

Accordingly, with regard to FIG. 10, a single signal may be spread bySF=2. Thus, the same structure as applying SFBC/FSTD by 4-subcarrierunit for a CDM-multiplexed signal may be used without consideringspreading as in FIG. 1.

FIG. 11 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to spread signals in a communication systemin accordance with one embodiment of the present invention. Inaccordance with the present invention, a same signal can be repeatedlytransmitted to obtain additional diversity. In particular, the samesignal may be repeatedly transmitted at least once via differentsubcarriers on a frequency axis, i.e., for a period of the same timeunit.

Referring to FIG. 11, an antenna set is determined as follows inaccordance with the present invention. After a signal has been spreadwith SF=2, a plurality of the spread signals are multiplexed. An antennaset is then determined by 2-subcarrier unit to enable the spread signalto be transmitted via the same antenna set. In this case, the signal isrepeatedly transmitted by changing an antenna set in case of repetitivetransmission to apply the SFBC/FSTD scheme for obtaining the 4-degreetransmitting antenna diversity. Accordingly, an antenna-frequencymapping structure, to which the SFBC/FSTD scheme for obtaining 4-degreetransmitting antenna diversity gain is applied, is repeated by4-subcarrier unit.

In FIG. 11( a), shown is an example where the repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 9.In FIG. 11( b), shown is an example where the repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 10.In particular, FIG. 11( a) and FIG. 11( b) illustrate examples forapplying the SFBC/FSTD scheme using four neighbor subcarriers,respectively. Notably, FIGS. 11( a) and 11(b) differ from each otherwith respect to the antennas included in the first and second antennasets, but use the same method in applying the described embodiment.

FIG. 12 is a diagram illustrating another example of a method forapplying an SFBC/FSTD scheme to spread signals in a communication systemin accordance with one embodiment of the present invention. In FIG. 12,like the embodiment shown in FIG. 11, after a plurality of signalsspread with SF=2 have been multiplexed, an antenna set is determined by2-subcarrier unit to enable the spread signals to be transmitted via thesame antenna set. Here, the signal may be repeatedly transmitted bychanging an antenna set in case of repetitive transmission to apply theSFBC/FSTD scheme for obtaining the 4-degree transmitting antennadiversity.

However, unlike the embodiment shown in FIG. 11 wherein the SFBC/FSTDscheme is applied through the four neighbor subcarriers, the embodimentof FIG. 12 uses a subcarrier having a prescribed interval by comparing asubcarrier used for repetitive transmission to that of a previoustransmission. Notably, it is preferable that subcarriers through which aspread signal sequence is multiplexed and transmitted includesubcarriers that neighbor each other.

In FIG. 12( a), shown is an example where a repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 9.In FIG. 12( b), shown is an example where a repetitive transmissionmethod is applied to the embodiment described with reference to FIG. 10.Notably, FIGS. 12( a) and 12(b) differ from each other with respect tothe antennas included in the first and second antenna sets but use thesame method in applying the described embodiment.

Accordingly, the embodiment of FIG. 12 may be described as follows.First, a one-time transmission is first performed using two of foursubcarriers to which an SFBC/FSTD scheme is applied. The one-timetransmission is then carried out using two of four subcarriers to whicha next SFBC/FSTD scheme is applied. In this case, an antenna setdifferent from that of a previous transmission is used to implement theSFBC/FSTD scheme.

FIG. 13 is a diagram illustrating an example of a method for applying anSFBC/FSTD scheme to at least one spread signal in a communication systemin accordance with one embodiment of the present invention. Preferably,if an antenna-frequency mapping structure according to the SFBC/FSTDtransmission scheme shown in FIG. 1 is maintained collectively for eachOFDM symbol or subframe on a system, then the rest of an SFBC antennaset unused in the SFBC/FSTD scheme of FIG. 12 may be used for anotherdata transmission.

Referring to FIG. 13, the same antenna-frequency mapping structure inthe SFBC/FSTD scheme for obtaining 4-degree transmitting antennadiversity gain by the 4-subcarrier unit (described with reference toFIG. 1) is used. Accordingly, two different multiplexed signals may betransmitted using this structure. Here, each of the multiplexed signalsis a multiplexed signal spread by SF=2, and can be transmitted throughtwo subcarriers.

As applied, in the SFBC/FSTD transmission scheme for transmitting arandom multiplexed signal generated from multiplexing a plurality ofspread data signals, a second antenna set other than a first antenna setto be SFBC-coded can be used to transmit another multiplexed signal.Moreover, by repeatedly transmitting the multiplexed signals via thefirst and second antenna sets, the multiplexed signals may respectivelybe transmitted through the different antenna sets. Hence, a 4-degreetransmitting antenna diversity effect may be obtained.

For example, a first multiplexed signal is transmitted via first antennaset and a second multiplexed signal is transmitted via second antennaset. In case of a repetitive transmission, mapping between a multiplexedsignal and an antenna is changed. Accordingly, the second multiplexedsignal will be transmitted via the first antenna set, while the firstmultiplexed signal is transmitted via the second antenna set. In case ofa next repetitive transmission, the mapping between the multiplexedsignal and the antenna is changed again to perform the correspondingtransmission. Thus, the first multiplexed signal will again betransmitted via first antenna set and the second multiplexed signal willagain be transmitted via second antenna set. Accordingly, iftransmission is performed in the above-mentioned manner, resources areefficiently used. Moreover, the antenna-frequency mapping structure inthe SFBC/FSTD scheme described with reference to FIG. 1 will bemaintained.

In the example above, the signal spread by SF=2 is transmitted via asingle OFDM symbol only. If so, repetition on a frequency axis ispossible to obtain additional frequency diversity. However, using asingle OFDM symbol is merely exemplary for illustrating the presentinvention. As mentioned in the foregoing description of SF=4, thepresent embodiment is applicable to a case of using several OFDMsymbols.

When transmitting via several OFDM symbols, repetition on a time axis aswell as a frequency axis is applicable to obtain diversity in additionto transmitting antenna diversity. The above embodiments are provided toexplain applications of the present invention and are also applicable toa system using an SFBC/FSTD transmission diversity method regardless ofvarious spreading factors (SF), various OFDM symbols numbers andrepetition counts on time and frequency axes.

FIG. 14 is a diagram illustrating an example of a method fortransmitting a spread signal in a mobile communication system inaccordance with one embodiment of the present invention. Referring toFIG. 14, a transmitting end spreads a signal using a plurality ofspreading codes (S1402). The plurality of spreading codes have aspreading factor of 4. The transmitting end codes the spread signal formultiple antenna transmission (S1404). The transmitting end multiplexesthe coded spread signal by code division multiplexing per each antenna(S1406). The transmitting end transmits the multiplexed signal via fourneighboring frequency resources of one OFDM symbol of a first antennaset consisting of two antennas (S1408). The transmitting end transmitsthe same multiplexed signal via four neighboring frequency resources ofone OFDM symbol of a second antenna set consisting of two antennas(S1410). The multiplexed signal transmitted via the first antenna setand the multiplexed signal transmitted via the second antenna set aretransmitted via respectively different OFDM symbols. The multiplexedsignal transmitted via the first antenna set and the multiplexed signaltransmitted via the second antenna set are separated from each other ina frequency domain.

FIG. 15 is a diagram illustrating an example of a method for receiving aspread signal in a mobile communication system in accordance with oneembodiment of the present invention. Referring to FIG. 15, a receivingend receives multiplexed signal via four neighboring frequency resourcesof one OFDM symbol, the multiplexed signal being transmitted from afirst antenna set consisting of two antennas of a transmitting end(S1502). The receiving end receives the same multiplexed signal via fourneighboring frequency resources of one OFDM symbol, the same multiplexedsignal being transmitted from a second antenna set consisting of twoantennas of the transmitting end (S1504). The multiplexed signaltransmitted via the first antenna set and the multiplexed signaltransmitted via the second antenna set are transmitted from thetransmitting end via respectively different OFDM symbols. Themultiplexed signal is obtained at the transmitting end from a codedspread signal using code division multiplexing per each antenna. Thecoded spread signal is obtained at the transmitting end by coding aspread signal between the two antennas in the first antenna set and thesecond antenna set.

FIG. 16 is a diagram illustrating an example of a base station and auser equipment in a mobile communication system in accordance with oneembodiment of the present invention. Referring to FIG. 16, the basestation (BS) (1600) includes one or more antennas (1602), a radiofrequency unit (1604), and a processor (1606) and the user equipment(UE) (1610) includes an antenna (1612), a radio frequency unit (1614),and a processor (1616).

Embodiments of the present invention can be implemented by variousmeans, e.g., hardware, firmware, software, and any combination thereof.In case of the implementation by hardware, a method of transmitting aspread signal in a communication system according to one embodiment ofthe present invention can be implemented by at least one of applicationspecific integrated circuits (ASICs), digital signal processors (DSPs),digital signal processing devices (DSPDs), programmable logic devices(PLDs), field programmable gate arrays (FPGAs), a processor, acontroller, a microcontroller, a microprocessor, etc.

In case of implementation by firmware or software, a method oftransmitting a spread signal in a communication system according to oneembodiment of the present invention can be implemented by a module,procedure, function and the like capable of performing the abovementioned functions or operations. Software code is stored in a memoryunit and can be driven by a processor. The memory unit is providedwithin or outside the processor to exchange data with the processor byvarious means known in public.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

What is claimed is:
 1. A method of transmitting Acknowledgement/NegativeAcknowledgement (ACK/NACK) information at a base station in a mobilecommunication system, the method comprising: generating a plurality offirst spread ACK/NACK information using a plurality of spreading codeswith a spreading factor of 4; coding the plurality of first spreadACK/NACK information for multiple antenna transmission to generate aplurality of first coded ACK/NACK information; summing the plurality offirst coded ACK/NACK information per each antenna port to generate afirst set of multiplexed ACK/NACK information; and transmitting thefirst set of multiplexed ACK/NACK information, wherein each first spreadACK/NACK information is coded so as to be mapped as shown in Table 1:TABLE 1 first set of available neighboring resource elements in oneorthogonal frequency-division multiplexing (OFDM) symbol antenna port Aa₁ a₂ a₃ a₄ antenna port B −a₂*  a₁* −a₄*  a₃* antenna port C 0 0 0 0antenna port D 0 0 0 0 wherein the “*” symbol represents a conjugateoperation, and a₁ to a₄ represent first to fourth elements of each firstspread ACK/NACK information.


2. The method of claim 1, further comprising: generating a plurality ofsecond spread ACK/NACK information using the plurality of spreadingcodes with the spreading factor of 4, wherein the plurality of firstspread ACK/NACK information and the plurality of second spread ACK/NACKinformation carry identical ACK/NACK information; coding the pluralityof second spread ACK/NACK information for the multiple antennatransmission to generate a plurality of second coded ACK/NACKinformation; summing the plurality of second coded ACK/NACK informationper each antenna port to generate a second set of multiplexed ACK/NACKinformation; and transmitting the second set of multiplexed ACK/NACKinformation, wherein each second spread ACK/NACK information is coded soas to be mapped as shown in Table 2: TABLE 2 second set of availableneighboring resource elements in one OFDM symbol antenna port A 0 0 0 0antenna port B 0 0 0 0 antenna port C b₁ b₂ b₃ b₄ antenna port D −b₂* b₁* −b₄* −b₃* wherein b₁ to b₄ represent first to fourth elements ofeach second spread ACK/NACK information.


3. The method of claim 2, wherein the first set of available neighboringresource elements are separated from the second set of availableneighboring resource elements by a plurality of subcarriers in afrequency domain.
 4. The method of claim 2, wherein the first set ofmultiplexed ACK/NACK information and the second set of multiplexedACK/NACK information are transmitted on different OFDM symbols.
 5. Themethod of claim 1, wherein the antenna ports A and B are consecutivelynumbered antenna ports, and the antenna ports C and D are consecutivelynumbered antenna ports.
 6. The method of claim 1, wherein the antennaports A and B are odd-numbered antenna ports, and the antenna ports Cand D are even-numbered antenna ports.
 7. A method of communicatingAcknowledgement/Negative Acknowledgement (ACK/NACK) information in amobile communication system comprising a user equipment (UE) and a basestation (BS), the method comprising: generating, by the BS, a pluralityof first spread ACK/NACK information using a plurality of spreadingcodes with a spreading factor of 4; coding, by the BS, the plurality offirst spread ACK/NACK information for multiple antenna transmission togenerate a plurality of first coded ACK/NACK information; summing, bythe BS, the plurality of first coded ACK/NACK information per eachantenna port to generate a first set of multiplexed ACK/NACKinformation; transmitting, by the BS, the first set of multiplexedACK/NACK information; and receiving, by the UE, the first set ofmultiplexed ACK/NACK information, wherein each first spread ACK/NACKinformation is coded so as to be mapped as shown in Table 1: TABLE 1first set of available neighboring resource elements in one orthogonalfrequency-division multiplexing (OFDM) symbol antenna port A a₁ a₂ a₃ a₄antenna port B −a₂*  a₁* −a₄*  a₃* antenna port C 0 0 0 0 antenna port D0 0 0 0 wherein the “*” symbol represents a conjugate operation, and a₁to a₄ represent first to fourth elements of each first spread ACK/NACKinformation.


8. The method of claim 7, further comprising: generating, by the BS, aplurality of second spread ACK/NACK information using the plurality ofspreading codes with the spreading factor of 4, wherein the plurality offirst spread ACK/NACK information and the plurality of second spreadACK/NACK information carry identical ACK/NACK information; coding, bythe BS, the plurality of second spread ACK/NACK information for themultiple antenna transmission to generate a plurality of second codedACK/NACK information; summing, by the BS, the plurality of second codedACK/NACK information per each antenna port to generate a second set ofmultiplexed ACK/NACK information; transmitting, by the BS, the secondset of multiplexed ACK/NACK information; and receiving, by the UE, thesecond set of multiplexed ACK/NACK information, wherein each secondspread ACK/NACK information is coded so as to be mapped as shown inTable 2: TABLE 2 second set of available neighboring resource elementsin one OFDM symbol antenna port A 0 0 0 0 antenna port B 0 0 0 0 antennaport C b₁ b₂ b₃ b₄ antenna port D −b₂*  b₁* −b₄* −b₃* wherein b₁ to b₄represent first to fourth elements of each second spread ACK/NACKinformation.


9. The method of claim 8, wherein the first set of available neighboringresource elements are separated from the second set of availableneighboring resource elements by a plurality of subcarriers in afrequency domain.
 10. The method of claim 8, wherein the first set ofmultiplexed ACK/NACK information and the second set of multiplexedACK/NACK information are transmitted on different OFDM symbols.
 11. Themethod of claim 7, wherein the antenna ports A and B are consecutivelynumbered antenna ports, and the antenna ports C and D are consecutivelynumbered antenna ports.
 12. The method of claim 7, wherein the antennaports A and B are odd-numbered antenna ports, and the antenna ports Cand D are even-numbered antenna ports.
 13. A base station for use in amobile communication system, the base station comprising: a radiofrequency unit configured to transmit a radio frequency signal; and aprocessor operably coupled to the radio frequency unit and configuredto: generate a plurality of first spread ACK/NACK information using aplurality of spreading codes with a spreading factor of 4; code theplurality of first spread ACK/NACK information for multiple antennatransmission to generate a plurality of first coded ACK/NACKinformation; sum the plurality of first coded ACK/NACK information pereach antenna port to generate a first set of multiplexed ACK/NACKinformation; and transmit the first set of multiplexed ACK/NACKinformation, wherein each first spread ACK/NACK information is coded soas to be mapped as shown in Table 1: TABLE 1 first set of availableneighboring resource elements in one orthogonal frequency-divisionmultiplexing (OFDM) symbol antenna port A a₁ a₂ a₃ a₄ antenna port B−a₂*  a₁* −a₄*  a₃* antenna port C 0 0 0 0 antenna port D 0 0 0 0wherein the “*” symbol represents a conjugate operation, and a₁ to a₄represent first to fourth elements of each first spread ACK/NACKinformation.


14. The base station of claim 13, wherein the processor is furtherconfigured to: generate a plurality of second spread ACK/NACKinformation using the plurality of spreading codes with the spreadingfactor of 4, wherein the plurality of first spread ACK/NACK informationand the plurality of second spread ACK/NACK information carry identicalACK/NACK information; code the plurality of second spread ACK/NACKinformation for the multiple antenna transmission to generate aplurality of second coded ACK/NACK information; sum the plurality ofsecond coded ACK/NACK information per each antenna port to generate asecond set of multiplexed ACK/NACK information; and transmit the secondset of multiplexed ACK/NACK information, wherein each second spreadACK/NACK information is coded so as to be mapped as shown in Table 2:TABLE 2 second set of available neighboring resource elements in oneOFDM symbol antenna port A 0 0 0 0 antenna port B 0 0 0 0 antenna port Cb₁ b₂ b₃ b₄ antenna port D −b₂*  b₁* −b₄* −b₃* wherein b₁ to b₄represent first to fourth elements of each second spread ACK/NACKinformation.


15. The base station of claim 14, wherein the first set of availableneighboring resource elements are separated from the second set ofavailable neighboring resource elements by a plurality of subcarriers ina frequency domain.
 16. The base station of claim 14, wherein the firstset of multiplexed ACK/NACK information and the second set ofmultiplexed ACK/NACK information are transmitted on different OFDMsymbols.
 17. The base station of claim 13, wherein the antenna ports Aand B are consecutively numbered antenna ports, and the antenna ports Cand D are consecutively numbered antenna ports.
 18. The base station ofclaim 13, wherein the antenna ports A and B are odd-numbered antennaports, and the antenna ports C and D are even-numbered antenna ports.19. A mobile communication system including a user equipment (UE) and abase station (BS), the BS comprising: a first radio frequency unitconfigured to transmit a radio frequency signal; and a first processoroperably coupled to the first radio frequency unit and configured to:generate a plurality of first spread ACK/NACK information using aplurality of spreading codes with a spreading factor of 4; code theplurality of first spread ACK/NACK information for multiple antennatransmission to generate a plurality of first coded ACK/NACKinformation; sum the plurality of first coded ACK/NACK information pereach antenna port to generate a first set of multiplexed ACK/NACKinformation; and transmit the first set of multiplexed ACK/NACKinformation; and the UE comprising: a second radio frequency unitconfigured to receive a radio frequency signal; and a second processoroperably coupled to the second radio frequency unit and configured tocontrol the second radio frequency unit to: receive the first set ofmultiplexed ACK/NACK information, wherein each first spread ACK/NACKinformation is coded so as to be mapped as shown in Table 1: TABLE 1first set of available neighboring resource elements in one orthogonalfrequency-division multiplexing (OFDM) symbol antenna port A a₁ a₂ a₃ a₄antenna port B −a₂*  a₁* −a₄*  a₃* antenna port C 0 0 0 0 antenna port D0 0 0 0 wherein the “*” symbol represents a conjugate operation, and a₁to a₄ represent first to fourth elements of each first spread ACK/NACKinformation.


20. The mobile communication system of claim 19, wherein the firstprocessor is further configured to: generate a plurality of secondspread ACK/NACK information using the plurality of spreading codes withthe spreading factor of 4, wherein the plurality of first spreadACK/NACK information and the plurality of second spread ACK/NACKinformation carry identical ACK/NACK information; code the plurality ofsecond spread ACK/NACK information for the multiple antenna transmissionto generate a plurality of second coded ACK/NACK information; sum theplurality of second coded ACK/NACK information per each antenna port togenerate a second set of multiplexed ACK/NACK information; and transmitthe second set of multiplexed ACK/NACK information; and the secondprocessor is further configured to: receive the second set ofmultiplexed ACK/NACK information, wherein each second spread ACK/NACKinformation is coded so as to be mapped as shown in Table 2: TABLE 2second set of available neighboring resource elements in one OFDM symbolantenna port A 0 0 0 0 antenna port B 0 0 0 0 antenna port C b₁ b₂ b₃ b₄antenna port D −b₂*  b₁* −b₄* −b₃* wherein b₁ to b₄ represent first tofourth elements of each second spread ACK/NACK information.


21. The mobile communication system of claim 20, wherein the first setof available neighboring resource elements are separated from the secondset of available neighboring resource elements by a plurality ofsubcarriers in a frequency domain.
 22. The mobile communication systemof claim 20, wherein the first set of multiplexed ACK/NACK informationand the second set of multiplexed ACK/NACK information are transmittedon different OFDM symbols.
 23. The mobile communication system of claim19, wherein the antenna ports A and B are consecutively numbered antennaports, and the antenna ports C and D are consecutively numbered antennaports.
 24. The mobile communication system of claim 19, wherein theantenna ports A and B are odd-numbered antenna ports, and the antennaports C and D are even-numbered antenna ports.